Effect of Grading Fingerling Hybrid Catfish (♀ Channel Catfish × ♂ Blue Catfish) on Growth, Production, Feed Conversion, and Food Fish Size Distribution

Abstract

Hybrid catfish (♀ Channel Catfish Ictalurus punctatus × ♂ Blue Catfish I. furcatus) production ponds often produce a wide size range of fish, and payments to farmers may be reduced due to discounts for larger fish. In general, fish under 1 lb or over 4 lb may decrease the price paid to farmers, but this is highly dependent on individual processors. The present study was conducted to determine the effect of grading hybrid catfish fingerlings on the size distribution of harvested food fish. Three 0.25-acre ponds were stocked with ungraded fingerlings (average weight = 0.05 lb; coefficient of variation [CV] = 78.0%) at 8,000 fish/acre. An additional three 0.25-acre ponds were stocked with double-graded fingerlings of the same average weight (0.05 lb) as the ungraded fingerlings but with a significantly reduced size variation (CV = 26.9%). Grading of the fingerlings had no significant effect on any production variable other than final size variation (ungraded fingerlings: CV = 48.2%; graded fingerlings: CV = 26.1%). Final mean weights were identical (1.1 lb) and feed conversion ratios were nearly identical (1.58 and 1.57) between the treatments. Survival and net production were similar between treatments. Overall, 13.5% of ungraded fish and 1.2% of graded fish were less than 0.5 lb at harvest; 5.6% of the ungraded fish and 0.1% of the graded fish were larger than 2.0 lb. Grading of hybrid catfish fingerlings is an effective means of decreasing food fish size variability without impacting production efficiency.

Effects of Density on Production of Hybrid Catfish in Intensively Aerated Earthen Ponds where Dissolved Oxygen is Not a Limiting Factor

“…Survival was similar in the two treatments (P = 0.26; Table 1), averaging 96.3% in the low-density ponds and 92.5% in the high-density ponds, typical for single-batch hybrid catfish in small research ponds Torrans and Ott 2018). The relative size variation within populations was similar at the two fish densities (Table 1; CV [mean ± SE] = 38.5 ± 1.1% in the low-density treatment and 39.1 ± 2.6% in the high-density treatment; P = 0.84), and although the size distribution in the high-density treatment was shifted to the left due to the smaller average fish weight (Table 1; Figure 1), the two curves were fairly similar.…”

“…A partial selective harvest of large fish during the summer (Mischke et al. ) will reduce the number of large fish produced overall but will also reduce the total yield; stocking of graded fingerlings will reduce the number of both large and small fish at harvest (Torrans and Ott ).…”

Performance of Channel Catfish and Hybrid Catfish in Single‐Batch, Intensively Aerated Ponds

“…Unharvested fish continue to grow and may exceed the preferred harvest size; large fish (>4 lb) fetch a lower farm‐gate price, and this has become a significant problem when using hybrids as the basis for catfish production (Mischke et al. ; Torrans and Ott ). Although these issues are inherent to all catfish operations using hybrid catfish, they are more problematic on nonintegrated, small‐ and medium‐sized farms (farms that are forced to sell catfish on the open market as opposed to farms that own processing plants).…”

“…The inability of processing plants to accommodate all hybrid production during that preferred harvest period results in delayed harvest of market-sized fish, which increases the risk of fish loss, limits cash inflows, and necessitates leaving many fish unharvested. Unharvested fish continue to grow and may exceed the preferred harvest size; large fish (>4 lb) fetch a lower farm-gate price, and this has become a significant problem when using hybrids as the basis for catfish production (Mischke et al 2017;Torrans and Ott 2018). Although these issues are inherent to all catfish operations using hybrid catfish, they are more problematic on nonintegrated, small-and medium-sized farms (farms that are forced to sell catfish on the open market as opposed to farms that own processing plants).…”

Evaluation of a Portable Electrosedation System for Anesthetizing Mature Channel Catfish

“…). Torrans and Ott () estimated that over 50% of the U.S. catfish industry consisted of hybrid catfish production. Hybrid catfish production involves seining, handling, transportation to the hatchery, injecting, checking the fish for ovulation during latency, crowding, handling, stripping, and transportation back to the ponds, all of which can be stressful to the fish.…”